Sound filter for loudspeakers



Filed Sept. 17, 1936 am a INVEN T'OR.

l'dwardggpermj ATTORNEYS Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE 5 Claims.

This invention relates to acoustical devices and comprehends a sound clarifier or filter which, while not necessarily restricted to such use, is primarily designed and intended for application to loud speakers of radio receiving sets, audible annunciator systems or the like.

The invention broadly comprehends a device of the indicated character which when applied to the speaker unit functions to filter and clarify the sounds or tones emitted therefrom by minimizing harshness, distortion, static or interference while serving to generally improve the quality of the sounds or tones.

More particularly the invention contemplates a device of the character set forth which is so constructed and arranged as to provide an annular chambered member for intercepting a portion of the sounds or tones emitted by a loud speaker and for acting thereupon to filter and clarify the same so as to improve the quality thereof by removing therefrom, or minimizing static, interference, distortion or other undesirable properties.

As a further feature the invention provides a sound or tone clarifier or filter which is comparatively simple in its construction, inexpensive to produce and install and which is highly efficient for its intended purpose.

With the above enumerated and other objects in View, reference is now made to the following specification and accompanying drawing in which there is disclosed by way of example a preferred embodiment thereof while the appended claims cover variations and modifications which fall Within the scope of the invention.

In the drawing:

Fig. 1 is a front view of a device constructed in accordance with the invention in applied position to a loud speaker of a radio receiving set and partially broken away to disclose the underlying structure.

Fig. 2 is a vertical sectional view therethrough taken on a plane indicated approximately by the line 2-2 in Fig. 1.

Fig. 3 is a perspective of the device as viewed from the rear and showing the same removed from the speaker.

Referring to the drawing by characters of reference, Ii designates generally a cone type dynamic loud speaker corresponding to those now generally used in radio receiving sets and which includes the usual conical diaphragm l i.

The clarifier or filter constituting the present invention includes a flat annular forward wall it! which is provided with a plurality of perforations 53 and which is formed with a rearwardly directed marginal rim M1 at the outer free edge thereof which rim is provided with an inwardly directed flange I5 at the free edge. A tube is is secured to and extends rearwardly from the inner marginal edge of the annular wall 52 and is of greater length than the rim it so as to protrude substantially therebeyond. A flexible resilient annular diaphragm l? is secured to and surrounds the tube intermediate its ends with the marginal edge thereof normally in contact with the forward face of the rim flange H5, The diaphragm is provided with circumferentially spaced notches l8 in the outer edge thereof which are of a depth to be exposed from the rim flange l5 and thereby provide sound or tone passages leading into the annular chamber 49 which is defined between the diaphragm ii, the forward wall E2, the rim l l and the tube 6, the portion of the tube which extends rearwardly beyond the diaphragm being provided with perforations 28.

The device is preferably completely constructed of parchment or vellum paper and as illustrated in the present instance, the rim Hi and flange it are disclosed as being constructed of separate strips of material secured to each other and to the forward wall 82 by adhesive tape 2%, while the tube It which is also of a separate strip of material, is similarly connected with the forward wall by adhesive tape 22. The device is applied to the speaker unit by adhesively securing the rear surface of the rim flange it to the usual washer or gasket 23 surrounding the margin of the speaker diaphragm H.

In its applied position, it will be observed that the rear end of the tube It is disposed in close proximity to the forward surface of the speaker diaphragm H and While a portion of the sounds or tones emitted pass directly through the tube 56, the remainder pass through the perforations 2i), thence through the passages defined by the notches i8 and through the perforations it in the forward wall l2 after entering the annular chamber E9. The diaphragm W is flexible and resilient and being free at its outer edge is capable of vibration.

The construction and arrangement described function in use to intercept a portion of the sound waves emitted by the spea er unit and serve to filter out distortion, static, interference or other undesirable qualities thereby removing the harshness as a result thereof and producing a more natural tone possessing the richness, roundness and mellowness of the sounds originally propagated.

What is claimed is:

1. A sound clarifler for loud speaker units or the like including an annular perforated filter element, a rearwardly directed marginal rim at the outer edge of said element provided with an inwardly directed flange at the free edge thereof, a tube extending rearwardly through the inner marginal edge of said filter element, a flexible resilient diaphragm secured to and surrounding said tube with a marginal edge thereof normally in contact with the forward face of the said flange, the said diaphragm provided With notches in the outer edge thereof of a size to be exposed from the flange, and said tube having perforations in the portion thereof extending rearwardly beyond the diaphragm.

2. A sound clarifler for loud speaker units including a perforated filter element having a marginal rim and provided with a central aperture, a tubular element secured at its forward end Within the said aperture and projecting rear- Wardly therefrom, and a flexible resilient diaphragm mounted upon said tubular element in surrounding relation thereto and in spaced relation from the perforated filter element to provide a chamber defined by said diaphragm, perforated filter element, rim and tubular extension.

3. A sound clarifler for loud speakers including a perforated filter element having a rearwardly directed marginal flange and a central aperture therein, a tubular element secured at its forward end in said aperture, and a flexible diaphragm mounted upon said tubular element in surrounding relation and spaced from the said filter element, and with its free marginal edge spaced from the said flange.

4. A sound clarifier for loud speakers including a perforated filter element having a rear- Wardly directed marginal flange and a central aperture therein, a tubular element secured at its forward end in said aperture, a flexible diaphragm mounted upon said tubular element in surrounding relation and spaced from the said filter element, with its free marginal edge spaced from the said flange, said tubular element extending rearwardly beyond the said flange and having perforations in the portion thereof extending therebeyond, and said diaphragm being provided with notches in the free edge thereof.

5. A sound clarifier for acoustical amplifying units comprising a casing defining a sound filtering chamber and including a perforated forward Wall and a flexible resilient rear Wall freely mounted at its outer edge to permit the same to vibrate to form a sounding diaphragm.

EDWARD SPERLING. 

